Since a cycloolefin resin obtained by polymerizing polymerizable monomers including a cycloolefin monomer in the presence of a metathesis polymerization catalyst is excellent in electric characteristics, mechanical characteristics, impact resistance, weather resistance and the like, the resin has been in progress on the way to practical applications of molded products in wide open fields.
A cycloolefin resin has been preferably employed as an electric insulating material of a printed wiring board or the like due to its excellency in electric characteristics. In recent years, the printed wiring board has been multilayered and high-density. When a wiring layer of such printed wiring board is formed with a solder or the like, an electric insulating material requires solder dip resistance. The solder used for forming the wiring layer is desirably of a lead free material from the viewpoint of environmental safety. Since the lead free solder contains a metal higher in melting point than lead, requirement for heat resistance of an electric insulating layer has further enhanced.
For instance, disclosed in WO 98/05715 A1 is a crosslinked resin molded product excellent in heat resistance obtained in a procedure in which a crosslinkable resin composition containing a thermoplastic norbornene resin, an organic peroxide and a crosslinking assistant is dissolved into a proper solvent if necessary, the composition is molded into a film or a prepreg, which is a resin molded product, then, the film or the like is laminated on a substrate such as a metal foil, and thereafter the laminate is heat-press molded, crosslinked and heat fused.
Submitted in Japanese Patent Application Laid-Open No. 2000-72859 is a suggestion that in a polymerization of a cycloolefin monomer in the presence of a metathesis polymerization catalyst, a compound having one vinyl group in the molecule such as a styrene derivative is mixed in the monomer for the purpose of adjusting a molecular weight.